Thermal relay switch



Jan. 19, 1943. E. J. LEUTHOLD THERMAL RELAY SWITCH Filed Aug. 22, 19590m TT N N R Wu m m vd. A R

Patented Jan. 19, 1943 THERMAL RELAY SWITCH Edgar J. Leuthold, Newark,N. J., assignor to Tung-Sol Lamp Works Inc., Newark, N. J., a

corporation of Delaware Application August 22, 1939, Serial No. 291,282

13 Claims.

, The present invention relates to thermal switches.

One object of the invention is an improved switch of this characterwhich is of simple, sturdy construction and is efficient in operation.

A further object of the invention is to provide a novel and improvedswitch of this type which may be economically manufactured and yet willbe of durable and compact construction.

A further object of the invention is to provide a novel switch of thistype which will have a positive snap action in operation.

Other objects and features of the invention will be apparent a thedescription proceeds.

Of the accompanying drawing,

Fig: 1 is a plan view of a switch embodying the invention and arrangedfor alternate variation of the series resistance of two circuits;

Fig. 2 is a side view of the device of Fig. 1;

Fig. 3 is a plan view representing another embodiment of the invention;and

Fig. 4 is a view showing four positions of the movable element of theswitch to illustrate the operation thereof according to one embodiment.

Referring to Figs. 1 and 2, the switch comprises a rectangular frame 2of conducting material of any suitable sheet metal, with the sidemembers indicated at 2' and the end members at 3. The frame 2 is mountedand fastened at one end upon a bracket 6 which in turn is mounted uponand secured to an insulating base 8. The other or free end of the frameis biased and operated from one position to the other by one or moreexpansible wires, and in the embodi ment of Fig. 1 by two such wires Iand H.

The latter are connected to the free end in any 1 bracket 6 in anysuitable manner, as for example by a flat leaf-spring I6 which iscentrally mounted on the bracket 6 and has its ends socured to the beadsl3 and I4 by means of short lengths of wire I] which are welded at oneend to the spring and have their other ends embedded in the beads.

The movable element 2 of the switch carries a bowed flexible strip orvane I3 which is secured to the free end 3 of frame 2, and also in theparticular embodiment shown to the other end of the frame. In theparticular embodiment shown the vane I8 is formed separately from .thememher 2 and welded to the end parts 3, with the van slightly longerthan necessary to bridge the ends 3 and bowed outwardly from the planeof the frame as shown in Fig. 1. Contacts l3 and 20 are centrallylocated on opposite sides of the strip l8 and co-operating contacts 2|and 22' carried by screws 2| and 22, mounted in screw brackets 23 and 24respectively, are positioned to be engaged by the contacts i9 and 20respectively upon biasing or swinging movement of the frame 2. When thefree end of frame 2 is in the position indicated in Fig. 1, contact 20on strip I8 is in engagement with the contact on screw 22. Clockwisemovement of the free ,end of the frame 2 (Fig. 1) about the fastened endcauses strip I8, assisted by pressure exerted by screw 22, to snap tothe opposite bowed position, at which time contacts l9 and 2| are inengagement and contacts 20 and 22' are out of engagement. In Fig. 4 areshown the various approximate positions assumed by the strip |8 duringthe above described movement of the frame in a clockwise direction fromthe position shown in Fig. 1 to the final position shown in Fig. 4, fora particular adjustment and mounting. When the frame moves back to theposition of Fig. 1 the reverse movement of strip i8 occurs with snapopening of contacts l9 and 2| and closure of contacts 20 and 22.

Movement of frame 2 is controlled in response to expansion andcontraction of wires I0 and I2 as will now be explained. A battery 26,or other source of electromotlve force, is electrically connected tobracket 6 and thence through vane It to lamps and 29 or other devices,the current through which is to be varied by the device. The lamps 2Band 29 are connected on one side to screw brackets 23 and 24respectively, with their other, terminals connected to ground, and. one

side of the battery is also connected with the will also flow from thebattery through bracket 6, strip i8, wire I0, resistance 30, bracket 23and lamp 28 to ground. This current, because of the inclusion of wire inand resistance 30 will be insufiicient to light the lamp 23 but willheat wire l causing it to expand and release the tension on the frame 2.Wire |2 (assisted by the half of spring H5 connected thereto throughbead M) will then cause the frame to swing about its pivot into thefinal position indicated in Fig. 4. C- sure of contacts l9 and 2| cutswire l0 and resistance 30 out of the circuit of lamp 28, which willconsequently burn brightly and opening of contacts and 22' causes thecurrent through lamp 29 to be reduced by the inclusion of wire l2 andresistance 3| in the circuit thereof. Wire ||l being thus cut out of thecircuit of lamp 28 cools and contracts and wire |2 being thus includedin the circuit of lamp 29 heats and expands until the reverse operationoccurs and the parts return to the position of Fig. 1. Thus with thevarious elements properly adjusted, the frame will continue to swingback and forth, causing alternate illumination of the lamps so long asthe battery is connected to the device.

Where equal periods of operation of each lamp or other device aredesired and the resistance of the lamps is the same, resistances 30 and3| should be of equal value and the lengths and tensions of wires l0 andI2 should be the same. The various elements are in proper balance if,when no current is supplied to the device and the screws 2| and 22 arewithdrawn sufficiently to be out of engagement with the strip I8, theframe 2 is held in a plane half way between the two operating positionswith the strip l8 bowed to either side depending upon the position itwas last in. The screws 2| and 22 are then advanced equally until one orthe other touches a contact on strip 18 and causes slight movement ofthe strip into substantially the second position shown in Fig. 4 ifcontacts 20 and 22 are in engagement or into the position reversethereto if contacts l9 and 2| are in engagement.

The device of Figs. 1 and 2 when adjusted and proportioned as abovedescribed will give equal periods of illumination to each lamp as theheating effect is the same on each wire irrespective of the voltage ofthe battery. This illuminating period of the lamps may be varied asdesired either by change in voltage, or of distance between the screwcontacts or by variation of the resistances 30 and 3|. If unequalperiods of iilumination are desired the tension of the wires l0 and I2may be adjusted initially or the resistance 30 and 3| can be madeunequal.

In the particular embodiment of Fig. l, the frame 2 is provided with apin 4 at its fastened end which is journalled in the bracket 8, but itis understood that any other suitable mounting for the biased frame 2may be provided.

In the embodiment of Fig. 3, the frame 2 is biased in one direction by aspring l2 which is connected between the movable end of the frame 2 anda bracket 32 on the insulating base 8. Wire I0 is connected between themovable end of the frame 2 and a bracket 34 on the base 8, to whichlatter bracket is also connected one end of resistance 30. With thedevice of Fig. 3 the tension of wire Ill when the wire is cold should besufiicient to overcome that of the spring |2' to hold the frame in theposition shown in the drawing. When in this position, if the battery 26is connected, current flows to lamp 29 because of the closure ofcontacts 20 and 22' and current flows through wire I0, resistance 30 andlamp 28 in series. Expansion of wire I0 due to the heating effect of thecurrent therethrough permits spring i2 to swing the frame into the otherposition with consequent opening of contacts 20 and 22' and closure ofcontacts l9 and 2|. The circuit for lamp 29 will now be open completelyand increased current will flow through lamp 28. The shunting of wireill by contacts I! and 2| permits cooling and consequent contraction ofthe wire and return of the frame to its initial position. Thus, as withthe device of Figs. 1 and 2, the frame will continue to oscillate backand forth so long as voltage is supplied to the device. The rate atwhich the device operates will depend, of course, upon the voltage ofthe battery, the tension of wire I0 and spring l2 and the resistance ofthe circuit. The periods of illumination of the lamps may be made equalor different as desired as in the case of the device of Figs. 1 and 2.

The invention has now been described in connection with two embodimentsthereof. In each a biased frame member 2 of the construction showncarries the bowed vane III which is buckled or snapped over from oneposition to the other to control a circuit and the movement of thecontact making part of the vane is in a direction opposite to that ofthe frame member.

The improved switch, in each embodiment, has been described andillustrated as controlling the circuits of lamps but it will beunderstood that lamps are illustrative only. Other elements or circuitsmay be controlled by the device, and the switch may be used generally asa thermal relay or thermally operated switch.

The following is claimed:

1. In a thermal switch, a sheet metal frame element comprising a pair ofparallel spaced arms joined by an end cross member and carrying a vanebowed out of the plane of and disposed between the arms of the frameelement and joined to the end member, said frame element togetherwiththe vane being mounted and fastened at the opposite end, anexpansible wire connected with said element at a point adjacent saidcross member and tending to move the same about the mounted end, acontact controlled by said vane and means for energizing said expansiblewire.

2. In a. thermal switch, a sheet metal frame element comprising a pairof parallel spaced arms joined by an end cross member and carrying avane bowed out of the plane of and disposed between the arms of theframe element and joined to the end member, said frame element togetherwith the vane being mounted and fastened at the opposite end, anexpansible wire connected with said element at a. point adjacent saidcross member and tending to move the same about the mounted end, acontact controlled by said vane and means for energizing said expansiblewire, the contact being carried by the vane member at a pointintermediate its ends and the vane member moving oppositely to the frameelement in the contact controlling operation thereof.

3. In a thermal switch, a sheet metal frame element having a pair ofspaced parallel arms joined at their ends by a cross member and a vanemember bowed out of the plane of and disposed between the arms of saidelement and joined to said cross member, means for mounting said elementand said vane at one end and biasing the same for movement of the otherend perpendicularly to the plane thereof including an expansible wireconnected at one end to the free end of said frame element. a contactcarried and controlled by said vane and means for energizing saidexpansible wire.

4. In a thermal switch, a sheet metal frame element having a pair ofspaced parallel arms joined at their ends by a cross member and a vanemember bowed out of th plane of and disposed between the arms of saidelement and joined to said cross member, means for mounting said elementand said vane at one end and biasing the same for movement of the otherend perpendicularly to the plane thereof including an expansible wireconnected at one end to the free end of said frame element, a contactcarried and controlled by said vane and means for energizing saidexpansible wire, the direction of movement of the vane being in theopposite direction to that of the frame element.

5. A device of the type described, comprising in combination a circuitto be controlled, an expansible resistance wire, a frame fixedly mountedat one end and secured at its other end to an end of said wire, saidframe having a centrally disposed vane bowed out from the plane of theframe, a contact on said vane and a fixed contact positioned to beengaged by the contact on said vane upon movement of said frame in onedirection, including spring means tending to move said frame to oneposition in opposition to the tension of said wire whereby when saidwire expands due to the passage of current therethrough the contacts arecontrolled by said spring means.

6. A device of the type described, comprising in combination a circuitto be controlled, an expansible resistanc wire, a frame fixedly mountedat one end and secured at its other end to an end of said wire, saidframe having a centrally disposed vane bowed out from the plane of theframe, a contact on said vane and a fixed contact positioned to beengaged by the contact on said vane upon movement of said frame in onedirection, including spring means tending to move said frame to oneposition in opposition to the tension of said wire whereby when saidwire expands due to the passage of current therethrough the contacts arecontrolled by said spring means, a second circuit to be controlled, asecond contact on said vane and a second fixed contact adapted to beengaged by said second contact on said vane upon movement of said frameunder infiuence of the contraction of said wire, and to be opened uponmovement of said frame in the opposite direction, said second fixedcontacts and said second contact on said vane being part of said secondcircuit to be controlled.

7. A device of the type described, comprising in combination a circuitto be controlled, an expansible resistance wire, a frame fixedly mountedat one end and secured at its other end to an end of said wire, saidframe having a centrally disposed vane bowed out from the plane of theframe, a contact on said vane and a fixed contact positioned to beengaged by the contact on said vane upon movement of said frame in onedirection, including spring means tending to move said frame to oneposition in opposition to the tension of said wire whereby when saidwire expands due to the passage of current therethrough th contacts arecontrolled by said spring means, a second circuit to be controlled, alsohaving an expansible resistance wire therein, said last mentioned wirebeing connected at one end to the movable end of said frame so as tooppose movement thereof upon contraction of said first mentioned wire, asecond contact carried by said vane and a second fixed contactpositioned to be engaged thereby upon movement of the frame in thedirection opposite to that causing closure of the first mentioned pairof contacts, said second contacts when in engagement shunting saidsecond expansible wire, said spring means comprising a member fixed atits center and insulatedly connected at each end with one of said wiresto provide the tension therein, whereby current flowing through one ofsaid wires will permit said spring means and the contraction of theother wire to move the frame into position to cause shunting of thecurrent carrying wire and the opening of the shunt about the other withconsequent continued oscillation of said frame.

8. In a thermal switch of the type wherein an expansible wire, whenheated by the passage of current therethrough, permits movement of anelement into position to shunt the wire and thereby cause the wire tocontract and cause movement of the element into non-shunting position,the improved combination comprising a frame mounted at one end formovements thereabout and connected at its other end to the expansiblewire, a bowed vane secured at its ends to said frame with the centralportion thereof bowed out from the plane of the frame, a contact carriedby said vane and a fixed contact positioned to be engaged by said firstmentioned contact upon movement of said frame about its mount, saidfixed contact serving to cause the bowed portion of said vane to moveoppositely to the direction of movement of said frame to give a snapaction opening and closing of the switch.

9. A device of the type described comprising in combination a pair ofcircuits to be controlled each including a fixed contact, a resistanceand an expansible wire in series, a movable member adapted in oneposition to cause a shunting of the resistance and wire of one circuitand in another position to cause shunting of the resistance and wire ofthe other circuit, said member comprising a frame pivoted at one end andhaving a central fiexible contact carrying strip adapted to snap fromone bowed position with the contact thereon engaging one of said fixedcontacts to another bowed position with the other contact thereonengaging the other fixed contact upon movement of the frame about itspivot, said expansible wire being connected under tension to the movableend of said frame to control the movement thereof by expansion andcontraction.

10. A device of the type described comprising in combination a pair ofcircuits to be controlled, each including a fixed contact, a resistanceand an expansible wire in series, a movable member adapted in oneposition to cause a shunting of the resistance and wire of one circuitand in another position to cause shunting of the resistance and wire ofthe other circuit, said member comprising a frame pivoted at one end andhaving a central flexible contact carrying strip adapted to snap fromone bowed position with the contact thereon engaging one of said fixedcontacts to another bowed position with the other-contact thereonengaging the other fixed contact upon movement of the frame about itspivot, said expansible wire being connected under tension to the movableend of said frame to control the movement thereof by expansion andcontraction, and resilient means insulatingly connected with said wiresto provide the tension therein.

11. A thermo-relay switch comprising in combination an insulating base,a conducting bracket on said base, a pin rotatably and verticallymounted in said bracket, a conducting frame secured at one end to saidpin, a buckled vane secured to said frame with the central portionthereof bowed out from the plane of the frame So as to snap back andforth through the frame upon oscillation thereof, a contact on the bowedportion of said strip, a contact ended screw carried by said base withthe contact end thereof positioned to be engaged by the contact on saidstrip upon movement of the frame in one direction, spring meansconnected to said frame tending to move the same toward contact closingposition, an expansible resistance wire electrically connected at oneend to said fixed contact and connected under tension at its other endto the movable end of said frame, said wire when cold preventingmovement of said frame by said spring means to contact closing position,whereby when a circuit including a source of electric motive force isconnected across the bracket and fixed contact current will flow throughsaid wire until the expansion thereof permits closure of said contactsby said spring means and the consequent shunting of said wire.

12. In a thermal switch structure of the character set forth, a sheetmetal frame mounted at one end for movement thereabout, an expansiblewire fastened to the free end of said frame and adapted to impart to andpermit movements of the free end of the frame in directions at rightangles to the plane thereof, said frame having a. bowed vane secured atits ends thereto and adapted to occupy two different positions withrespect to the frame, a contact carried by said vane, a stationarycontact engaged by said first named contact in one position of said vaneand said first named contact being adapted to be moved over out ofcontact with the fixed contact to a second position when the free end ofthe frame is moved in a direction to increase the pressure between thecontacts.

13. A device of the type described. comprising in combination a circuitto be controlled, an expansible pull wire, a frame fixedly mounted atone end, said pull wire being fastened at one end adjacent the free endof said frame, said frame being biased against the pull of said pullwire and having a buckling vane bowed out from the plane of the frame, acontact on said vane and a second contact positioned to be engaged bythe contact on said vane upon movement of said frame in one directionwhereby the contraction and expansion of said pull wire together withthe bias of said frame control said contacts.

EDGAR J. LEU'IHOLD.

